Heretofore, in the medical and printing plate-making fields, effluent generated by the wet process of image forming materials has resulted in problems for workability. In recent years, it has increasingly been demanded to reduce the processing effluent in view of environmental protection and space saving. Accordingly, silver salt photothermographic dry imaging materials capable of forming images by application of only heat have been practiced and increasingly employed in the aforesaid fields.
Silver salt photothermographic dry imaging materials themselves (hereinafter referred to as heat developable materials, photothermographic materials or simply as light-sensitive materials) were proposed a relatively long time ago (refer, for example, to Patent Documents 1 and 2).
This heat developable martial is processed employing a so-called thermal processor which applies constant heat onto heat developable materials to form images. As noted above, along with its rapid popularity in recent years, a large quantity of the above thermal processors have been offered on the market. On the other hand, depending on temperature and humidity, problems occur in which slippage properties between the light-sensitive material and conveying rollers of a thermal processor or processing members vary, resulting in unreliable conveyance as well as uneven density. Further, problems have occurred in which density of photothermographic materials varies over an elapse of time. It has been discovered that these phenomena are markedly generated in photothermographic materials which form images via heat development. Further, in recent years, a decrease in size of laser imagers as well as more rapid processing has been sought.
On that account, it has become essential that characteristics of photothermographic materials are enhanced. In order to achieve sufficient density even under rapid processing, it is effective to enhance covering power by increasing the number of color forming points, employing silver halide grains of a smaller average particle size as described in Japanese Patent Publication Open to Public Inspection (hereinafter referred to as JP-A) Nos. 11-295844 and 11-352627, to employ highly active reducing agents having a secondary or tertiary alkyl group as described in JP-A No. 2001-209145, or to employ development accelerators such as hydrazine compounds, vinyl compounds, as well as phenol derivatives or naphthol derivatives (refer to Patent Documents 3 and 4). However, in cases in which heat development and exposure are simultaneously performed, problems occur in which vibration in the exposed portion tends to be transferred to heat development portion due to the fact that the exposed portion is adjacent to the heat deployment portion. Trials have been made to stabilize conveyance by improving this point (refer to Patent Documents 5 and 6). On the other hand, as improvements from aspect of light-sensitive materials, techniques are disclosed in which in order to improve conveying characteristics during heat development and to minimize pin holes, surface roughness is controlled (refer to Patent Document 7).
(Patent Document 1) JP-A No. 2002-278017 (claims)
(Patent Document 2) JP-A No. 2003-066558 (claims)
(Patent Document 3) JP-A No. 2002-162692 (claims)
(Patent Document 4) JP-A No. 2004-085763 (claims)
(Patent Document 5) JP-A No. 2003-287862 (claims)
(Patent Document 6) JP-A No. 2004-004279 (claims)
(Patent Document 7) JP-A No. 2001-005136 (claims)